The
fossil fuel industry’s emissions of a powerful greenhouse gas are
dramatically higher than previously thought.

Researchers
who pulled together the biggest database yet of worldwide methane
emissions found that, after natural sources were discounted,
emissions from gas, oil and coal production were 20-60% greater than
existing estimates.

Methane
makes up just 16% of global greenhouse gases and is shorter-lived
than the CO2 which accounts for three quarters, but has a much more
powerful warming effect.

The
extra methane estimated by the study is 300 times larger than the
amount leaked in California’s Aliso Canyon last year, which was the
worst gas leak in US history. While bad news for efforts to tackle
climate change, the new study published in Nature also found that
methane emissions had fallen as a fraction of industry’s
production.

Lead
author Stefan Schwietzke, of the University of Colorado and US
science agency Noaa, said that methane from fossil fuels had played a
significant role in global warming, but the gas’s short lifetime
meant acting on it now could pay quick dividends.

“The
good news is that reducing methane emissions now will reduce climate
forcing in only a few years – it takes much longer for CO2. And
since fossil fuel methane emissions are higher than previously
thought, the potential to reduce climate forcing from this specific
source is also greater,” he told the Guardian.

Experts
said the study meant scientists should reconsider their climate
models. “Emissions scenarios currently used for climate prediction
need to be reassessed taking into account revised values for
anthropogenic methane emissions,” wrote Dr Grant Allen of the
University of Manchester in a commentary in Nature.

Other
studies have suggested the huge growth in the US shale gas industry
is to blame for a spike in methane emissions since the mid-noughties.
But the new work found methane emissions from natural gas production
had declined as a fraction of production from 8% in the mid-1980s to
around 2% in the late 2000s and early 2010s.

“There
has been anecdotal evidence for a while that the oil and gas industry
improved their efficiency. Our data confirms this anecdotal evidence
on a global scale,” said Schwietzke.

Emissions from the fossil fuel industry contribute 30 to 45% of atmospheric methane

Fossil fuels
Coal mines, power stations, oil rigs 30 to 45%

Biological activityWetlands, landfill, agriculture 55 to 70%

0%

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Guardian graphic | Source: Nature

Methane
emissions have been rising since the industrial revolution but paused
between 1996 and 2006 – believed by some to be because of decreased
fossil fuel emissions in former Soviet Union countries – before
marching upwards again. Most is from natural sources, such as
wetlands and geological seepage, but humanity’s share is estimated
to account for 30-45% of the total.

The
study published on Wednesday examined the isotopic “fingerprints”
of methane sources, compiling thousands of measurements from public
sources and peer-reviewed papers. Allen said it was the largest
database of its kind.

Schwietzke
said that such models on methane were very sensitive to the data that
informed them. “A key message is that the number and
comprehensiveness of measurements matter.”